A circularly polarized horn antenna is used for transmitting and receiving circularly polarized signals for wireless communication, radar, and imaging applications. Such horns are typically easy to design and fabricate for microwave frequency bands. But for millimeter wave (mm-wave) and terahertz frequency applications, micro-fabrication techniques are needed for such fabrications, which can make them expensive. The immediate application of the antenna is for mm-wave wireless communication. The antenna would be relevant for a variety of sub-mm-wave and terahertz bands, as the communication and imaging applications gain interest and popularity at these frequencies.
Currently, the technology used for circularly polarized horns are 1) by using a septum (or waveguide partitions, discontinuities and irises) and 2) by using an orthogonal mode transducer (OMT). The former uses a metallic partition within the waveguide section for linear-polarization to circular-polarization conversion. The partition contains sub-wavelength (small) features that require precise fabrication, alignment and placement within the waveguide. Even with existing micro-/nano-fabrication methods, it is a challenging task for sub-mm-wave and terahertz frequency designs. This is due to the shrinking dimensions of the waveguides (1 mm or less thickness) and small features of the partition itself. Ultimately, the design becomes expensive and sensitive to fabrication tolerances rendering it not very viable for high frequency applications. The latter technique (i.e., OMT) requires rigorous assemblies of waveguide sections, requiring 3D metal fabrication techniques with high precision and low surface roughness. Again, fabrication of such 3-dimensional waveguide networks is challenging and expensive for high frequency applications owing to small dimensions.